Directional sensitivity of the retina: 75 years of Stiles–Crawford effect

Abstract

The reduction of the brightness when a light beam's entry into the eye is shifted from the centre to the edge of the pupil has from the outset been shown to be due to a change in luminous efficiency of radiation when it is incident obliquely on the retina. The phenomenon is most prominent in photopic vision and this has concentrated attention on the properties of retinal cones, where responsibility has yet to be assigned to factors such as differences in shape, fine structure and configuration, and membrane anchoring of photopigment molecules. Geometrical optics and waveguide formulations have been applied to the question of how light is guided in receptors, but details of their geometry and optical parameters even if they become available will make calculations complex and of only moderate generality. In practice, the diminution of oblique light helps visual performance by reducing deleterious influence of ocular aberrations and of glare caused by light scattering when the pupil is wide. Receptor orientation can come into play in ocular conditions due to mechanical disturbance and has been shown to have potentiality as a tool for clinical diagnosis. Currently, open questions include microanatomical and molecular differences between rods and cones, the coupling of the optical image of the eye with the transducing apparatus in the photoreceptors, possible phototropism and more convincing methods of estimating the actual spatial distribution of photon events as it affects visual resolution.

Müller cells separate between wavelengths to improve day vision with minimal effect upon night vision

“…3d). We also applied our algorithm to cones and found it to match perfectly previous results for light propagation along these cells 23,[40][41][42] , which were obtained and examined by other methods such as coupled mode theory 22,[43][44][45] .…”

Changes in color vision with decreasing light level: separating the effects of normal aging from disease

“…The effect of pupil size changes on effective retinal illuminance can also be confounded with the associated changes in directional sensitivity of cones [34,35]. The Stiles-Crawford effect is difficult to account for accurately when the area of the retina stimulated is not restricted to the fovea [36] and when the entry pupil location for peak maximum sensitivity is not known [37].…”

Dynamic near-infrared imaging reveals transient phototropic change in retinal rod photoreceptors

“…The SCE is exclusively observed in cones, which can benefit good vision quality by suppressing intraocular stray light under photopic conditions. 2 In contrast, the SCE has not been detected in rods, which dominate scotopic vision. 2 In other words, the absorption efficiency of light by rods was not affected by the incident angle in early SCE studies which were performed with psychophysical methods.…”